Can hot weather stop the spread of bird flu in US dairy cattle?

A Michigan dairy farm worker has become the second confirmed case of a person infected by the influenza A(H5) virus in the US, federal authorities confirmed on May 22.

According to the Michigan Department of Health and Human Services, the worker had been regularly exposed to infected livestock and tested positive for influenza A(H5) – of which H5N1 is a subtype – and experienced mild symptoms but have since recovered.

This is the second confirmed case of a human infection with bird flu in US history. The first case was reported in March when a Texas dairy farmworker was diagnosed after being in close contact with infected cows. The worker’s only symptom was eye redness (conjunctivitis).

The Centers for Disease Control and Prevention (CDC) has maintained that the risk to the public remains low, though those who have been exposed to infected animals are at a higher risk.

Why is this important?

Since the start of the outbreak in Spring, dairy farmers have been told to bolster their biosecurity,​ including PPE wearing and isolating herds from potential sources of infection, such as water troughs or ponds.

Experts have warned that taking preventative measures is key to ensuring the virus does not acquire dangerous mutations that would increase its transmissibility to humans.

WHO’s chief scientist warned​ that previous cases of bird flu in humans globally have had high mortality rates while vaccination efforts haven’t advanced sufficiently at this point. According to CDC, human infections with HPAI A(H5N1) virus have been reported in 23 countries since 1997, resulting in severe pneumonia and death in about 50% of cases.